package com.acme.task3;

import java.util.Scanner;

public class Task3Arrays {
	public static void main(String[] args) {
		for (int i = 1; i <= 50; i++) {
			if (i % 3 == 0) System.out.println(i);
		}
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int[] ma = new int[n];
		for (int i=0; i<n; i++){
			ma[i]=i;
		}
		System.out.println(avg(ma,n));
		
	}	
	public static double avg(int [] ma, int n){
		double result=0;
		for (int i=0; i<n; i++){
			result=result+ma[i];
		}
			return result/n ;
		}
}
